Immunization has been used for over a hundred years to protect humans and animals against disease. The premise of traditional immunization is that the most effective immune responses to an antigen, or a pathogen containing the antigen, occur after an individual is challenged with that same antigen two or more times. This phenomena is called immunological memory or a secondary immune response. When the immunization is successful, the individual is protected from the effects of the pathogen from which the antigen was derived.
For example, once an individual is successfully immunized with an antigen derived from a bacterial organism, the immune system in that individual is primed and ready to respond to that bacteria when it is encountered. Successful immunization requires that the antigen is located on an area of the bacteria that is accessible to the individual's immune system. When successful, the immune system responds, the bacteria is killed, contained, neutralized, or otherwise cleared from the body, and little or no disease results from the infection by the bacterial organism. The key to this protection is that immunization with the antigen must occur prior to the exposure to the bacterial organism from which the antigen is derived.
Accordingly, the traditional immunization process generally includes injecting an antigen into an individual, waiting an appropriate amount of time, and allowing the individual to mount an immune response. The time required for mounting an immune response is between approximately two weeks and several months for most antigens. In most cases, a booster administration of the antigen is required to maintain the immune response. This booster is normally given weeks or months after the initial administration of the antigen.
Therefore, traditional immunization is highly successful at providing protection if given several months in advance of exposure to an antigen, or pathogen, but traditional immunization is of little use when an individual is exposed to a new antigen to which the individual has not been previously exposed and an immediate effective immune response is required. A good example of such a situation is military troops in need of protection from bioterrorism agents. While a population of individuals can be vaccinated against agents of bioterrorism in advance of any potential exposure to the agents, traditional vaccination is not a simple answer. Traditional vaccination of a population creates harmful reactions in some persons and there is potential that the population may never be exposed to the agent, yet risks were taken. Additionally, a government cannot logistically develop, produce and vaccinate essential personnel with vaccines for every possible agent of bioterrorism. Accordingly, what is needed is a composition that can be administered either immediately before, or even after, an individual's contact, or suspected contact, with a pathogen, which administration allows for the generation of an immediate protective or effective immune response in the individual.
As alluded to above, another shortcoming of traditional immunization procedures is the requirement that the infectious pathogen, or a portion of the infectious pathogen, be administered to an individual. There are numerous incidences wherein vaccinations have themselves caused illness and even death because they contain a pathogen or a portion of a pathogen. Accordingly, what is needed is a composition that can be administered to an individual for immunization that does not contain a portion of the pathogen against which the individual is being immunized.
Still another shortcoming of traditional immunization procedures is the requirement that separate immunization procedures be used for each antigen, although in some cases several antigens are included in a single procedure. These separate immunization procedures are required because the natural memory, or secondary, immune responses are specific for the antigen to which the primary immune response was directed. Accordingly, what is needed is a “universal immunogen” that can be administered to an individual that will prime the individual's immune system for an immune response and a means to direct this immune response to new targets as the need arises. Alternatively, there is a need for the means to re-direct an existing immune response to a new target. Such a “universal immunogen,” or the means of re-directing an existing immune response, would reduce the number of immunizations currently recommended for individuals.